A Few Good Replacements For Diseased Phlox And Coneflowers

I’ve nearly finished putting the gardens to bed for the winter. As I worked, I actually did go through with my pledge to rip out all those diseased coneflowers and phlox that have been limping along in agony for years. Aster yellows, powdery mildew; I’m as tired of looking at that ick as they are of having it. So they’re out of their misery now, and so am I.

Phlox paniculata ‘Purple Kiss’

The upside is, I get to buy new plants next spring to take their places. I can live without coneflowers, but I would miss phlox in the garden. So I hunted around for some truly standout mildew-resistant varieties. Below is some information on the ones that got the best reviews from fellow master gardeners and local garden designers.

Phlox Flame™ Series: The naturally dwarf cultivars in the Flame series have outstanding mildew resistance. Available in a wide array of colors, these phlox have an attractive bushy habit that’s nicer looking than that of other phlox varieties. Zones 3 – 8.

Phlox Candy Store™ Series: Phlox in the Candy Store series were bred specifically to have a compact habit, as well as good mildew resistance. Blooms are as vibrant as their names suggest: ‘Grape Lollipop’, ‘Bubble Gum Pink’ and ‘Coral Crème Drop’. Zones 4 – 9.

Phlox paniculata ‘Purple Kiss’: This pretty phlox also got high marks for mildew resistance. Though some gardeners I talked to did say that mildew problems can happen when ‘Purple Kiss’ is planted in a spot with too little sun and/or air circulation. Zones 4 – 9.

Phlox Flame Series™ Purple

Phlox paniculata ‘David’: If you like white flowers, ‘David’ is the mildew-resistant phlox for you. I’ve had this problem-free phlox in my garden for years and I can’t think of one bad thing to say about it. Zones 4 – 9.

Phlox paniculata ‘Lord Clayton’

And here is a short list of the runners up: Phlox Junior Dance™ (Phlox paniculata ‘Junior Dance’), Phlox paniculata ‘Lord Clayton’, Phlox paniculata ‘Robert Poore’ and Phlox paniculata ‘Starfire’.

Coneflower Conundrum
Replacing a diseased phlox with a better-performing variety doesn’t sting too much. But it’s painful to dig up coneflowers that offer so much long-lasting color in spite of aster yellows without knowing what to put in their place. Talking with other gardeners, it quickly became clear that a lot of us are trying to find good alternatives to coneflowers. Unfortunately, some of the plants at the top of people’s lists, including mine, are also highly susceptible to aster yellows, including black-eyed Susan, asters and sneezeweed (Helenium).

Globe Thistle
iStock

Coreopsis ‘Sienna Sunset’

But there are other late-summer bloomers to consider that either don’t get aster yellows or are less likely to be affected by it. Here is the list I’ve compiled so far: Agastache, butterfly weed (Asclepias tuberosa), Coreopsis ‘Sienna Sunset’, Gaillardia aristata ‘Fancy Wheeler’, globe thistle (Echinops ritro), Hoary vervain (Verbena stricta), Nepeta ‘Six Hills Giant’, Sea holly (Erngium spp.) and Zebrina tree mallow (Malva sylvestris ‘Zebrina’). 

A version of this story appeared in the November/December 2012 issue of Northern Gardener.